Removal of pesticide residues in food by ionizing radiation

ABSTRACT

The present disclosure relates to a process for removal of pesticide residues from aqueous solutions and food products by ionizing radiation. Standard pesticides concentrations recognized by international organizations as maximum residues limit (MRLs) were used as the targeted concentrations in both aqueous solutions and food products. Commercially known pesticides and recommended irradiation doses by International Atomic Energy Agency (IAEA) were selected for this investigation. Aqueous solutions and food products fortified with pesticide residues were subjected to selected doses of ionizing radiation. Radiation-induced removal of pesticide residues is generally greater in aqueous solutions than in food products. Ionizing radiation can reduce the residues of pirimiphos-methyl in potatoes, grapes and dates; malathion and cypermethrin in grapes to below MRLs at the recommended irradiation doses.

CLAIM OF PRIORITY

This application is a divisional application of U.S. patent applicationSer. No. 12/818,197 titled REMOVAL OF PESTICIDE RESIDUES IN FOOD BYIONIZING RADIATION filed on Jul. 23, 2010.

FIELD OF THE INVENTION

The present disclosure relates to a process to remove pesticide residuesremaining in the matrix of some vegetables and/or fruits by ionizingradiation.

BACKGROUND

Pesticides are used for controlling insects, weeds, fungi, and/or otherpests which destroy agricultural crops. Pesticides are widely used infruits and vegetables because of their susceptibility to insect anddisease attacks. Widespread use of pesticides in commercial agriculturehas led to an increase in farm productivity.

The rapid development of agriculture in Saudi Arabia has resulted in amarked increase in the use of pesticides in agriculture. Amongcommercial pesticides, organophosphorus (OPs) and synthetic pyrethroidare widely applied on vegetables and fruits to control pestsinfestation.

Since pesticides are potentially harmful to the environment andconsequently to human beings through the consumption of pesticidecontaminated food, governments and international organizationsestablished maximum residue limits (MRLs), based on the assumption thatgood agricultural practices are applied in the use of pesticides infarming, for pesticide residues in foodstuff (standard authority such asCodex Alimentarius Commission™ 2009 and World Health Organization™).When these chemical compounds are applied according to good agriculturalpractices, MRLs are not exceeded, but their incorrect application mayleave harmful residues, which involve possible health risk andenvironmental pollution. Therefore, residues of pesticides in foodproducts can affect the ultimate consumers especially when theseproducts are freshly consumed.

TABLE A Maximum Residue Limits (MRLs) in mg kg⁻¹ (ppm) for targetedpesticide residues in/on selected food products. Maximum residue limits(MRLs) Targeted pesticide Potatoes Onions Grapes Dates Malathion 0.5 8 88 Pirimiphos-methyl 0.05 1 1 0.1 Cypermethrin 0.05 0.1 2 Zero (Source:Codex Alimentarius Commission ™)

The total dietary intake of pesticide residues which remain onagricultural commodities are known as carcinogens (Cabello G et al. 2001and Mills P et al. 2005) and are very harmful toxins because of theirpotential long-term adverse affects (Bolognesi C, Morasso G 2000).

Residual pesticides on fresh vegetables and fruits decrease by variousculinary applications or with time, depending on the type and propertiesof the pesticides. Several investigators have found that levels of somepesticide residues were reduced by the pre-harvest intervals and/orculinary application, such as washing, peeling, cooking, boiling andstorage (Cengiz M et al. 2007).

Moreover, these techniques in some cases are unsuitable for removal ofresidual pesticides adhering to surfaces of vegetables and fruits and/orpresent in plant tissues (Sances F et al. 1992).

Ionizing radiation (gamma-ray, x-ray and electron beam) is an importanttechnology in food industry for preservation of a variety of fruits andvegetables (CAST, 1996). Low doses of ionizing radiation up to 1 kGy caninhibit sprouting in potatoes (Auda H, Khalaf Z 1979), onions (Elias P,Cohen A 1983); control the insects in dry fruits like dates (Azelmat Ket al. 2006) and improve the storability of grapes (Al-Bachir M 1999).Irradiation doses below 2 kGy have been used to prolong shelf-life offruits (Al-Bachir M 1999).

Medium doses (2-7 kGy) can improve technological properties of grapes(increase juice yield) and enhance anthocyanin extraction from grapes(Ayed N et al. 2000).

However, depending on the level of security required in commercialoperations, fruits can receive up to three times the minimum absorbeddose for disinfestations (Hallman G 2001). On this basis, irradiation to4-6 kGy can be used for decontamination (and disinfestation) incommercial processing of dates and can replace the currently establishedpractice of fumigation with highly toxic chemicals (Grecz N et al.1988).

TABLE B Absorbed doses accepted in USA by the Food and DrugAdministration ™ (FDA). Product Approved use Dose (kGy) White potatoesSprout inhibition 0.05-0.15 Fruits Disinfestations; ripening 1 (maximum)delay. Improving technology 2-7 properties (Grapes) Vegetables, freshDisinfestations 1 (maximum)

Ionizing radiation from electron beam accelerators or gamma ray sourcesis an efficient process for oxidation removal of organic pollutants.Compared to other Advanced Oxidation Process (AOPs), this technique hasthe advantage that no chemicals have to be added to the treated product.In addition, an alternative technique for the treatment of thewastewater is electron beam irradiation in combination with otherconventional treatment methods. In the electron beam process, theorganic materials react with the radicals generated by water radiolysisand the degradation products can be easily removed by conventionalbiological or chemical treatment (Pikaev A et al. 1997).

Irradiation of water by high-energy electrons or gamma rays results inthe formation of two reducing species, the aqueous electron e⁻ _(aq),and the hydrogen atom, H., and one oxidizing species, the hydroxylradical, .OH, according to Equation 1 (Spinks J, woods R 1990).

H2O-\/\/→[2.6]e−aq+[0.6]H.+[2.7].OH+[0.45]H2+[0.7]H2O2+[2.7]H30+  (1)

The number in brackets in Equation 1 is referred to as G values and arethe number of radicals, molecules, or ions that are formed (ordestroyed) in a solution absorbing 100 eV (energy). The effectiveness ofthis process in destroying organic compounds results from the rapidreaction of one or more of these species with the solute of interest.

The chemistry that is of principal importance with respect to the gammaradiolysis or electron beam processes in aqueous solutions and/or infood products is related to these three reactive species (i.e. e−aq, H.and .OH).

The major reaction in the water radiolysis involve the formation ofe−aq, .OH and H. and in the presence of oxygen also O2.-, reactiveintermediate, for example the reaction of e−aq and H. with O₂ is rapidand results in the formation of the super oxide ion-hydroxyl radicalsaccording to Equations 2 and 3 (Cooper J et al. 1993).

e−aq+O2→O2.-  (2)

H.+O2→HO2.  (3)

The effects of ionizing radiation on pesticides in aqueous solutions orin organic solvents are reviewed by many researchers (Abdel Aal E et al.2001, Basfar A et al. 2007, Basfar A et al. 2009, Drzewicz P et al.2004, Drzewicz P et al. 2004, Mohamed K et al. 2009 and Varghese R etal. 2006), but limited investigations of this nature have been performedfor irradiated food (Bachman S, Gieszczynska J 1982, Carp A et al. 1972,Carp A et al. 1972, Cichy R et al. 1979, Cin D, Kroger M 1982, Lan R atal. 1976, Lepine F 1991 and Solar J et al. 1971).

Fruits and vegetables form an important component of human diet. Beingrich sources of vitamins and minerals, fruits and vegetables add qualityto human diet and increase its nutritive value. For these reasons theyhave also been termed as protective foods. The water activity in mostfruits and vegetables is very high. Therefore, most fruits andvegetables are highly perishable. Fruits and vegetables play host toseveral micro-organisms and insect pests, supporting their growth andproliferation. Often fruits and vegetables harbor pathogens andparasites that may endanger human health. They may also harbor insect'spests of quarantine importance resulting in trade restrictions in exportmarkets. They may be also contaminated with pesticides because of theenvironmental and processing conditions under which they are produced.

Therefore, before they can be safely incorporated into other foodproducts, the pesticides load should be reduced. Because “thermaltreatment” can cause significant loss of flavor and aroma, a “coldprocess”, such as irradiation, is ideal. Research over the past 40 yearshas shown that irradiation can be used to destroy insects and parasitesin grains, dried beans, dried fruits and vegetables; to inhibitsprouting in crops such as potatoes and onions; to delay ripening offresh fruits and vegetables; to increase juice yield, and forimprovement of re-hydration. Moreover, food is irradiated to provide thesame benefits as when it is processed by heat, refrigeration, freezingor treated with chemicals to destroy insects, fungi or bacteria thatcause food to spoil or cause human disease and to make it possible tokeep food longer and in better condition in warehouses and homes.Irradiation has been proposed as an alternative to chemicals and otherconventional treatments. It is interesting to notice that thepre-harvest pesticides will still be used and their chemical interactionwith irradiation is unknown. Therefore, there is a chance thatirradiation may decontaminate pesticides residues in selected foodproducts.

SUMMARY

Embodiments of the present invention relate to a process for removingpesticide residues remaining in some kinds of vegetables and fruits byionizing radiation. In another embodiment, the fruits and vegetables areexposed to radiation ranging from 150 to 7000 Gy to remove thepesticides. This procedure may help preserve the quality of fruits andvegetables.

According to another embodiment, the removal of pesticides is done inaqueous solutions. In other embodiments, the process of AOPs, whichinvolve oxidation of pesticides by .OH radicals, such as radiolysis bygamma-rays, that provide novel degradation methods to remove thepesticides may be used. Ionizing radiation from electron beamaccelerators or gamma ray sources is considered to be an efficientprocess for oxidation removal of pesticides.

In one or more embodiments, pesticides Malathion, Pirimiphos-methyl andCypermethrin reduction level are measured as a result of irradiation ofvegetables and fruits. In another embodiment, a method of removingpesticide residues from vegetables and fruits by subjecting them toradiation to improve food quality and food safety may be used.

According to some embodiments vegetables such as potatoes and onions areirradiated and level of pesticides such as Malathion, Pirimiphos-methyland Cypermethrin are measured.

According to some embodiments, fruits such as dates and grapes areirradiated and level of pesticides such as Malathion, Pirimiphos-methyland Cypermethrin are measured.

According to some embodiment, the level of pesticides were measured todetermine if they were lower than the MRLs.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 shows removal rates of targeted pesticides at selectedconcentrations in distilled water and investigated vegetables at anabsorbed dose of 1000 Gy according to a method of Table 2.

FIG. 2 shows removal (%) of cypermethrin (0.05 ppm in potatoes and 0.1ppm in onions), pirimiphos-methyl (0.05 ppm in potatoes and 1 ppm inonions) and malathion (0.5 ppm in potato and 8 ppm in onions) indistilled water and investigated vegetables at an absorbed dose of 1000Gy according to a method of Table 2.

FIG. 3 shows removal rates of targeted pesticides at selectedconcentrations in distilled water and investigated fruits at an absorbeddose of 1000 Gy according to a method of Table 3.

FIG. 4 shows removal (%) of cypermethrin (2 ppm in grapes),pirimiphos-methyl (1 ppm in grapes and 0.1 ppm in dates) and malathion(8 ppm in grapes and dates) in distilled water and investigated fruitsat an absorbed dose of 1000 Gy according to a method of Table 3.

FIG. 5 shows removal (%) of targeted pesticides at selectedconcentrations in vegetables and fruits as a function of absorbed doseaccording to a method of Tables 2 and 3.

DETAILED DESCRIPTION

Pesticides reference materials (purity >98%) were purchased asindividual standards from Dr. Ehernstorfer (Augsburg, Germany). Chemicalstructure, trade and chemical names (IUPAC) as well as family and actionused for selected pesticides are as follows:

Malathion: Insecticide/acaricide (Organophosphate group).

O,O-dimethylphosphorodithioate, diethyl-mercaptosuccinate.

Pirimiphos-methyl: Insecticide (Organophosphate group).

O-(2-diethylamino-6-methylpyrimidin-4-yl) O,O-methyl phosphorothioate.

Cypermethrin: Insecticide (Synthetic pyrethroids group).

(RS)-α-cyano-3-phenoxybenzyl(1RS,3RS;1RS,3SR)-3-(2,2-dichlorovinyl)-2,2-methylcyclopropanecarboxylate.

Organic solvents (residue analysis grade) for dissolving, extracting andclean-up were acetone, ethanol, diethyl ether and petroleum etherpurchased from Merck (Germany) and Aldrich (UK). Anhydrous sodiumsulfate, sodium chloride and sodium hydrogen carbonate and florisil(80-120 mesh) were obtained from Sigma (UK). Pesticides aqueoussolutions were prepared in doubly distilled water further purified byBarnstead E-pure system (USA).

TABLE C List of chemicals used in this invention. No. Chemical Source 1Acetone Sigma-Aldrich, UK. 2 Acetonitrile Merck, Germany. 3 Anhydroussodium sulfate Sigma, UK. 4 Cypermethrin standard Ehernstorfer Quality(EQ), Augsburg, Germany. 5 Double distilled water Barnstead E-puresystem (USA) 6 Dichloromethane Sigma-Aldrich, UK. 7 Diethyl etherSigma-Aldrich, UK. 8 Ethanol Sigma-Aldrich, UK. 9 Ferrous ammoniumsulfate Sigma-Aldrich, UK. 10 Florisil (80-120 mesh) Sigma-Aldrich, UK.11 Hexane Sigma-Aldrich, UK. 12 Malathion standard Ehernstorfer Quality(EQ), Augsburg, Germany. 13 Petroleum ether (40-60) Sigma-Aldrich, UK.14 Pirimiphos-methyl standard Ehernstorfer Quality (EQ), Augsburg,Germany. 15 Sodium chloride Sigma-Aldrich, UK. 16 Sulfuric acidSigma-Aldrich, UK.

Stock standard solutions were prepared by exact weighing of pesticidereference material and dissolution in acetone. Working standardsolutions of pesticides for monitoring and irradiation studies werefreshly prepared by appropriate dilution with acetone. Stock standardsolutions and working standard solutions were stored under refrigerationat 4° C. (1 month of maximum storage time).

A Cobalt-60 gamma rays radiation source was used for all irradiationstudies. A Gamma Cell 220 (MDS Nordion, Canada) was calibrated usingaqueous ferrous sulfate (Fricke dosimetry) solution (ASTM StandardPractice E1026, 1997). The typical dose rate was 14.52 kGy h⁻¹ andtransit dose was estimated to be 5.86 Gy sec⁻¹. All of the irradiationswere conducted at room temperature, 23° C.

A Shimadzu 2010 series GC with QP2010 mass spectrometer and HP-5capillary column (Hewlett Packard, 30 m, 0.25 mm I.D., 0.25 μm filmthickness) was used for gas chromatography analysis. The helium carriergas velocity was 40 cm/s, high pressure injection was set at ON and highpressure and injection pressure were set at 250 kPa. The temperatures ofinjector, ion source and interface were set at 250° C., 200° C. and 250°C., respectively and the oven program was 2 minutes at 80° C., 20°C./minute to 180° C. (2 minutes) and 5° C./minute to 250° C. (5minutes). Ions were formed for mass spectrometric detection using ionelectron impact ionization (EI+) mode scan. EI+ mass spectra databasesearches were carried out using the Wiley Registry of Mass SpectralData, and the NIST Mass Spectral Search Program.

Aqueous solutions samples were analyzed according to the official methodadopted by (EPA, 1980 and Letizia et al., 1992). On the other hand,general official multi-residues analysis methods approved by federalagencies and organizations (Anonymous, A.O.A.C. Official Methods ofAnalysis, 2000) for analysis of pesticides residues in fresh vegetablesand fruits samples were implemented (monitored and irradiated). Gaschromatography in combination with mass selective detector (MSD) wasused for the parent compound analysis (identification andquantification) under the same mentioned conditions.

Recovery experiments were conducted in both aqueous solutions andconsidered food products. Malathion (0.5, 4 and 8 ppm),pirimiphos-methyl (0.05, 0.1, 1 and 2 ppm) and cypermethrin (0.05, 0.1and 2 ppm) were introduced in small volume of acetone into the distilledwater to prepare the desired concentrations. Check vegetables and fruitssamples (i.e. potatoes, onions, grapes and dates) were thoroughlyindividually mixed to obtain homogeneous samples. A malathion,pirimiphos-methyl and cypermethrin (0.05 to 0.5 ppm) were introduced insmall volume of acetone into the center of the check samples to preparethe desired two concentrations. Then, the fortified vegetables andfruits samples were analyzed and the recovery percentages werecalculated. The same extraction procedures and GC-MS conditions asapplied for samples analyses were used for recovery studies. Therecovery of these procedures for malathion, pirimiphos-methyl andcypermethrin pesticides was no less than 90% (distilled waterexperiments) and 75% (selected vegetables and fruits).

A total of 150 samples of different kinds of fresh fruits (grapes anddates) and vegetables (potatoes and onions) were collected at randomfrom a local supermarkets and/or grocery markets in Riyadh, Saudi Arabiaduring January to September. The samples taken included: 90 samples offruits and 60 samples of vegetables. Collected samples were subjected toanalysis and detection for considered pesticide residues using GasChromatography-Mass Spectrometer (GC-MS).

The invention involves a method for removal of pesticide residues invegetables and fruits. Chromatographic standard solutions of themalathion, pirimiphos-methyl and cypermethrin pesticides (100 ppm inacetone) were diluted to prepare the desired concentrations ofconsidered pesticide solutions in distilled water at 0.5 and 8 ppm(malathion), 0.05, 0.1 and 1 ppm (pirimiphos-methyl) and 0.05, 0.1 and 2ppm (cypermethrin), then the diluted concentrations solutions wereplaced in 40 ml vials having airtight caps with teflon based siliconsepta. On the other hand, collected vegetables (potatoes and onions) andfruits (grapes and dates) samples were coarsely ground individually in afood chopper to prepare required samples. Pesticide standard solutionsin acetone were introduced individually at desired concentrations intothe center of the targeted vegetables and fruits samples in each vial.Moreover, samples were thoroughly mixed to obtain homogeneous samples.Moreover, the prepared aqueous solutions and fortified samples ofvegetables and fruits were irradiated in vials at selected absorbeddoses over the range 150-7000 Gy using ⁶⁰Co gamma-rays. Therefore, theremoval percent of pesticides in aqueous solutions and selected foodproducts by gamma irradiation was calculated with different initialconcentrations of considered pesticides in relation with differentabsorbed doses.

It is important to mention that the pesticide concentrations wereselected based on maximum residue limits (MRLs) for targeted pesticidesin selected vegetables and fruits. In addition, absorbed doses wereselected based on accepted absorbed doses in USA by the Food and DrugAdministration. The following examples further illustrate the presentinvention.

EXAMPLES Example 1 Market Basket Survey

The pesticide residues detected in selected vegetable and fruit samplesare shown in Table 1.

TABLE 1 Pesticide residues range detected in selected vegetables andfruits. No. Positive Residues MRL Food of Detected samples range (mgproduct samples pesticide No. % (mg kg⁻¹) kg⁻¹) Potatoes 30 Malathion 320 0.031-0.072 0.5 (0.048^(a)) Pirimiphos- 2 0.018-0.025 0.05 Me(0.022^(a)) Cyper- 1   NDL-0.017^(b) 0.05 methrin Onions 30 Cyper- 13.33 NDL-0.02^(a) 0.1 methrin Dates 60 NDL 0 0 NDL NR Grapes 30 NDL 0 0NDL NR The numbers in parenthesis represent the residues average. NDL:no detectable level; NR: not reported. ^(a)amount monitored inpotatoes/onions pulp. ^(b)amount monitored in potatoes peel.

As shown in Table 1, out of the 150 investigated samples, 143 (95.3%)showed no pesticide residues while 7 (4.7%) contained residues belowMRLs. Therefore, no samples contained pesticide residues above MRLs. Inthree samples of potatoes, malathion, pirimiphos-methyl and cypermethrinresidues were detected with average concentrations of 0.048, 0.022 and0.017 ppm, respectively. One sample of onions contained 0.02 ppm ofcypermethrin, and no samples of grapes and dates contained residues ofinvestigated pesticides under detection limits.

Example 2 Irradiation of Aqueous Solutions

Removal (%) of pesticides in aqueous solutions at various absorbed dosesis shown in Table 2.

TABLE 2 Removal (%) of pesticides in aqueous solutions at variousabsorbed doses. Initial Targeted pesticides concentrations MalathionPirimiphos-Me Cypermethrin (ppm) (%) (%) (%) 0.05 NT 52^(a), 74.2^(b),95^(c), 0^(a), 8.6^(b), 13.8^(c), 100^(d), NT^(e,f) 28.4^(d), NT^(e,f)0.1 NT 38^(a), 46^(b), 77^(c), 0.0^(a), 5^(b), 7^(c), 11^(d), 96.6^(d),N.T^(e,f) NT^(e,f) 0.5 3.4^(a), 10.4^(b), 21^(c), NT NT 35.4^(d),N.T^(e,f) 1 NT 2^(a), 15^(b), 24.8^(c), NT 41.8^(d), 56.4^(e), 84.2^(f)2 NT NT N.T^(a,b,c), 0.22^(d), 3.65^(e), 22.1^(f) 4 0^(a), 0.43^(b),2.73^(c), NT NT 7.19^(d), NT^(e,f) 8 0^(a,b,c), 3.29^(d), NT NT11.97^(e), 30.77^(f) Absorbed dose: (^(a)150 Gy, ^(b)250 Gy, ^(c)500 Gy,^(d)1000 Gy, ^(e)2000 Gy and ^(f)7000 Gy). NT: not targeted.

As shown in Table 2, pesticide type, initial concentration, and absorbeddose play a significant role in the pesticide removal; this was evidentfrom the removal percentages after irradiation of pesticides in aqueoussolutions. In this respect, the higher the absorbed dose the higher thepesticide removal and vice versa. In addition, data reflect theimportant role of a variety of reactive species (mainly hydroxylradicals and solvated electrons) formed in irradiated aqueous solutionsin the reduction yield of pesticides. Moreover, the expected removalyields of pesticide residues in selected vegetables and fruits should bedecreased proportionally compared to aqueous solutions. This is due tothe fact that food items contain a large number of organic substanceswhich may compete with pesticide residues for a various reactive speciesgenerated by radiation in the selected food items matrix by radiation.This issue is important in extending bench scale aqueous solutionsresults to commercial irradiation of selected vegetables and fruits.

Example 3 Irradiation of Vegetables Potatoes and Onions

Removal (%) of pesticide residues in both aqueous solutions and selectedvegetables after irradiation up to 1000 Gy was measured. The results areshown in Table 3 and FIGS. 1, 2 and 5).

The data for removing pesticide residues of the present invention asshown in Table 3 and FIGS. 1, 2 and 5) demonstrate that the removal ofpesticides is greater in irradiated aqueous solutions than in selectedvegetables. The residues of the pirimiphos-methyl (0.05 ppm) in potatoeswere removed by 18% with absorbed dose of 1000 Gy, whereas a removal of100% was achieved with aqueous solution experiments at the same absorbeddose.

Moreover, no significant removal took place when irradiation wasperformed for onions fortified with pirimiphos-methyl (1 ppm), whereasremoval of 41.8% was observed with distilled water at the absorbed doseof 1000 Gy. In this respect, no measurable removal took place when gammairradiation was performed on potatoes and onions samples fortified withmalathion (0.5 and 8 ppm) and cypermethrin (0.05 and 0.1 ppm) at theabsorbed dose of 1000 Gy. On the other hand, a removal of (35.4 and3.29%) and (28.6 and 11%) was achieved with aqueous solution at the samepesticide concentrations and absorbed dose, respectively.

TABLE 3 Removal (%) of pesticide residues in aqueous solutions andselected vegetables after irradiation up to 1 kGy. Targeted Aqueoussolutions Vegetables concentration Concentration Removal ConcentrationRemoval Pesticide type MRL (ppm) (ppm) (%) (ppm) (%) Malathion 0.5^(P)0.323 35.4 NE 0 8^(O) 7.74 3.29 NE 0 Pirimiphos-Me 0.05^(P) BDL 1000.041 18 1^(O) 0.582 41.8 NE 0 Cypermethrin 0.05^(P) 0.036 28.6 NE 00.1^(O) 0.089 11 NE 0 P: potatoes. O: onions. BDL: below detection limitof 0.001 ppm. NE: no effect.

Example 4 Irradiation of Fruits Grapes and Dates

Removal (%) of pesticide residues in aqueous solutions and selectedfruits after irradiation up to 7000 Gy was measured. The results areshown in Table 4 and FIGS. 3-5.

TABLE 4 Removal (%) of pesticide residues in aqueous solutions andselected fruits after irradiation up to 7 kGy. Targeted Aqueoussolutions Fruits Absorbed concentration Concentration RemovalConcentration Removal Pesticide type dose (Gy) MRL (ppm) (ppm) (%) (ppm)(%) Malathion 1000 8^(D) 7.74 3.29 NE 0.0 8^(G) 2000 7.04 11.97 NE 0.07000 5.54 30.77 7.694 3.83 Pirimiphos-Me 1000   0.1^(D) 0.0034 96.60.056 44.4 1^(G) 0.582 41.8 NE 0.0 2000 0.436 56.4 0.941 5.9 7000 0.15884.2 0.809 19.1 Cypermethrin 1000 2^(G) 1.996 0.22 NE 0.0 2000 1.9273.65 NE 0.0 7000 1.558 22.1 1.948 2.6 ^(D)dates. ^(G)grapes. NE: noeffect.

As shown in Table 4 and FIGS. 3-5, the removal of pesticides is greaterin irradiated aqueous solutions than in selected fruits. No measurableremoval took place when gamma irradiation was performed on grapes spikedwith malathion (8 ppm), pirimiphos-methyl (1 ppm) and cypermethrin (2ppm) up to 2000 Gy (malathion and cypermethrin) and 1000 Gy(pirimiphos-methyl), whereas removal of 11.97 and 3.65% and 41.8% wasachieved with aqueous solution at the same absorbed doses and pesticideconcentrations, respectively. Gamma radiolysis showed that the residuesof the malathion (8 ppm) and cypermethrin (2 ppm) on grapes were reducedslightly with absorbed dose of 7000 Gy (7.694 ppm and 1.948 ppm with3.83% and 2.6% removal), respectively. Accordingly, a removal of 19.1%was achieved with pirimiphos-methyl (1 ppm) with absorbed dose of 7000Gy, whereas a removal of 84.2% was obtained with aqueous solutions. Inaddition, irradiation at an absorbed dose of 2000 Gy resulted in 5.9%removal for the initial 1 ppm of pirimiphos-methyl residues. Therefore,irradiation at absorbed doses of 2000 Gy (used commercially to improvegrapes storability) and 7000 Gy (used commercially to increase grapesjuice yield) can reduce the pesticide residues concentrations to levelsbelow MRLs of (pirimiphos-methyl) and (malathion, pirimiphos-methyl andcypermethrin) contaminated grapes, respectively.

Aqueous solutions gamma radiolysis experiments showed that the initialconcentrations of the malathion and pirimiphos-methyl (8 and 1 ppm) wereremoved slightly (3.29%) and moderately (41.8%) with absorbed dose of1000 Gy, respectively. No positive removal effect when irradiation wasperformed on dates spiked with malathion (8 ppm) at an absorbed dose of1000 Gy, whereas a removal of 3.29% was obtained with distilled water.In addition, irradiation at the same dose was sufficient to reducepirimiphos-methyl residues (0.1 ppm) in contaminated dates to below MRLreaching 40.32% and 48.47% removal, respectively (Ave. 44.40%) comparedwith a removal of 96.6% for aqueous solutions experiment.

The differences between distilled water and real samples data is due tothe fact that the various reactive species generated in investigatedvegetables and fruits by radiation become less available to react withtargeted pesticide residues. A large number of organic substancespresent in selected food items will compete with pesticides for thevarious reactive species generated by radiation in the targetedvegetables and fruits matrix. Thus, the removal yields obtained forpesticides in aqueous solutions were higher than those obtained incomplex matrices of targeted vegetables and fruits.

As mentioned in Examples 3 and 4 above, ionizing radiation can reducethe residues of pirimiphos-methyl (in potatoes, grapes and dates);malathion and cypermethrin (in grapes) to below maximum residue limits(MRLs).

Although the present embodiments have been described with reference tospecific example embodiments, it will be evident that variousmodifications and changes may be made to these embodiments withoutdeparting from the broader spirit and scope of the various embodiments.Accordingly, the specification and examples are to be regarded in adescriptive rather than a restrictive sense.

What is claimed is:
 1. A process, comprising: treating an organicmaterial, wherein the organic material is vegetables (potatoes andonions) and/or fruits (dates, and grapes), with a pesticide to reduce aconcentration of the pesticide in the organic material; irradiating theorganic material by an ionizing radiation to reducing a level of thepesticide to meet an acceptable level by a standard authority; andmeasuring the level of the pesticide after a gamma irradiation.
 2. Theprocess of claim 1, further comprising: removing a malathion pesticidein the potatoes by the ionizing radiation at an absorbed dose of 1000Gy, wherein the malathion pesticide in concentration of 0.5 ppm.
 3. Theprocess of claim 1, further comprising: removing a pirimiphos-methylpesticide in the potatoes by the ionizing radiation at an absorbed doseof 1000 Gy, wherein the pirimiphos-methyl pesticide in concentration of0.05 ppm.
 4. The process of claim 1, further comprising: removing acypermethrin pesticide in the potatoes by the ionizing radiation at anabsorbed dose of 1000 Gy, wherein the cypermethrin pesticide inconcentration of 0.05 ppm.
 5. The process of claim 1, furthercomprising: removing a malathion pesticide in the onions by the ionizingradiation at an absorbed dose of 1000 Gy, wherein the malathionpesticide in concentration of 8 ppm.
 6. The process of claim 1, furthercomprising: removing a pirimiphos-methyl pesticide in the onions by theionizing radiation at an absorbed dose of 1000 Gy, wherein thepirimiphos-methyl pesticide in concentration of 1 ppm.
 7. The process ofclaim 1, further comprising: removing a cypermethrin pesticide in theonions by the ionizing radiation at an absorbed dose of 1000 Gy, whereinthe cypermethrin pesticide in concentration of 0.1 ppm.
 8. The processof claim 1, further comprising: removing a malathion pesticide in thedates by the ionizing radiation at an absorbed dose of 1000 Gy, whereinthe malathion pesticide in concentration of 8 ppm.
 9. The process ofclaim 1, further comprising: removing a pirimiphos-methyl pesticide inthe dates by the ionizing radiation at an absorbed dose of 1000 Gy,wherein the pirimiphos-methyl pesticide in concentration of 0.1 ppm. 10.The process of claim 1, further comprising: removing a malathionpesticide in the grapes by the ionizing radiation at absorbed doses of1000, 2000 and 7000 Gy, wherein the malathion pesticide in concentrationof 8 ppm.
 11. The process of claim 1, further comprising: removing apirimiphos-methyl pesticide in the grapes by the ionizing radiation atan absorbed dose of 1000, 2000 and 7000 Gy, wherein thepirimiphos-methyl pesticide in concentration of 1 ppm.
 12. The processof claim 1, further comprising: removing a cypermethrin pesticide in thegrapes by the ionizing radiation at an absorbed dose of 1000, 2000 and7000 Gy, wherein the cypermethrin pesticide in concentration of 2 ppm.